Pheromones are chemicals released by an organism into its environment enabling it to communicate with other members of its own species.
Mealy bugs are known to spoil crops such as grapes, pears etc., especially the long tailed mealy bug. The long-tailed Mealybug is scientifically known as Pseudococcus longispinus (Targioni-Tozzetti).
The racemic form of the pheromone was synthesized synthetically by the Miller group after identifying the structure of isolated pheromone. Miller has published that 25 μg is sufficient to attract mealy bug for three months. When sprayed on crops, the male bugs are attracted and then they are killed. Male population is thus decreased.
Pheromones play an important role in chemical communication among organisms. Various chiral and non-racemic pheromones have been identified since the late 1960s. Their enantioselective syntheses were achieved so as to establish the absolute configuration of the naturally occurring pheromones and also to clarify the relationship between absolute configuration and the bioactivity of the chiral pheromones.
Synthesis of pheromones is an important and arising field of research to establish the structures and also to provide sufficient material to carry out biological studies. In general, natural pheromones are available in very limited quantities (usually in μg by killing several bugs) which restrict the extensive field trials. To overcome such constrain several methods have been reported in the literature to construct low molecular weight pheromones.
Accordingly Mori K et al. in Current Organic Synthesis, 2004, Vol. 1, No. 1 disclosed various aspects of pheromone synthesis where methodologies such as organoborane reactions, organotransition metal chemistry including olefin metathesis, asymmetric epoxidation, asymmetric dihydroxylation, other asymmetric chemical processes was demonstrated.
Recently, pioneering work from Miller's group led to the identification and synthesis of several interesting pheromones from mealybugs; particularly the article disclosed in Journal of Chemical Ecology, Vol. 31, No. 12, December 2005 discloses first example of monoterpenoid structural motif sex pheromone of the obscure mealybug, Pseudococcus viburni, consists of (1R*,2R*,3S*)-(2,3,4,4-tetramethylcyclopentyl)methyl acetate. Further highly irregular terpenoid structure, and the irregular terpenoid structures of related mealybug species, suggests that these insects may have unique terpenoid biosynthetic pathways.
Jocelyn G. Millar SYNLETT 2010, No. 15, pp 2319-2321 reported synthesis of pheromones involving Ireland-Claisen conditions in seven steps (scheme 1 below) also discloses commercial development for detection, monitoring, and control of longtailed mealybugs and the leafroll viruses that they vector.

Similarly, Yunfan Zou et al discloses synthesis of the Pheromone of the Longtailed Mealybug, a Sterically Congested, Irregular Monoterpenoid in J. Org. Chem. 2009, 74, 7207-7209 7207 with 13.5% overall yield wherein the key steps included regiospecific cyclization of an R-diazo-β-ketoester to build the cyclopentane ring, followed by reduction of the enol triflate of the ketone to place the double bond.
Article titled a new class of monoterpene structure by Jocelyn G. Millar et al. in Org. Lett., 2009, 11 (12), pp 2683-2685 deals with the sex pheromone of the longtailed mealybug, where 2-(1,5,5-trimethylcyclopent-2-en-1 yl)ethyl acetate was identified as a new monoterpenoid skeleton. A [2,3]-sigmatropic rearrangement was used in a key step during construction of the sterically congested tetraalkylcylopentene framework (cf below scheme 2).

Additionally Ezra Dunkelblum has developed a practical synthesis of the P. citri pheromone, using two ozonolysis steps and a selective reduction of an aldehydic group in a ketoaldehyde intermediate and the same is reported in IOBC wprs Bulletin Vol. 25, 2002.
In view of prior art, pheromones are usually obtained in μg to mg quantities which are insufficient for the determination of their absolute configuration as well as for the biological studies to examine their practicality in the field. Pheromone synthesis is therefore important in order to rigorously establish the structure of a new pheromone and also to provide a plenty of material to carry out extensive biological tests.
In view of the technical constraints such as poor yield, activity, complex stereocenteres and cumbersome resolution, the present inventors have developed efficient synthesis for preparation of biologically active and commercially viable enantiomers of sex hormones in high yield.